This invention relates to a measurement system for surface contours. Systems applying interferometry and holography exist to measure contours and deflections, respectively, on the order of wavelengths. Mechanical profiling systems exist which measure the contours of surfaces which are hard, can be touched, and are easily accessible. No system is known that can measure the surface shape of objects which have contours that vary more than wavelengths and are too soft, delicate, inaccessible, etc., to be touched by a probe.
The new system described here has variable sensitivity so it can measure deflections over the entire range that mechanical profiling systems can measure, but it does not have to touch the surface. This means surfaces such liquids, where touching the surface would invalidate the measurement, could be measured. Surfaces which are too soft for a mechanical probe could be measured because only light would be reflecting off the surface. Surfaces which are inaccessible to touch or where touching should be avoided such as electrically charged objects could still be measured. The new system allows noncontact measurements of objects which previously could not be measured, and it performs this function at a cost less than mechanical probe systems because the hardware for the new system is simpler and the inexpensive software is more sophisticated.
The following additional methods have all been tried and found wanting in some particular: shearography, projection moire, shadow moire, stereoscopic distance measurement, depth-of-focus distance measurement, reflecting of a finely focused beam, moire deflectometry, and grid projection with computer analysis.
This system is expected to be useful in quality control, prototyping, design, and as a research tool. The invention will not only allow some measurements to be made that could not previously be made, but it will be a cheaper alternative to expensive optical based profilers and delicate mechanical contact profiling systems. It will be cheaper because the expensive optics of optical based profilers and the delicate, expensive mechanisms involved in mechanical profilers would be replaced with an inexpensive light source, a simple CCD camera, and sophisticated software on a personal computer.